Baghdad -LRB- CNN -RRB- -- Seven police officers were killed and nine were injured Tuesday in a series of attacks at security checkpoints in the western Iraqi province of Anbar , police said .

The attacks happened in the town of al-Rutba , a predominantly Sunni Muslim community that for a few years was an al Qaeda stronghold after the 2003 U.S-led invasion of the country .

In Tuesday 's first attack , a suicide car bombing at a police checkpoint in northern al-Rutba killed four police officers and injured three others , said police officials in Ramadi , the provincial capital .

Gunmen later attacked several security checkpoints in the town , killing three police officers and wounding six , police said .

Information about the attackers ' casualties , beyond the suicide bomber , was n't available . Al-Rutba is about 435 kilometers -LRB- 270 miles -RRB- west of the country 's capital , Baghdad .

Also Tuesday , a car bomb exploded near a busy market in the central Iraqi town of Musayyib in Babil province , killing one person and injured 11 , police in Baghdad said .

Musayyib , a largely Shiite town , is about 70 kilometers -LRB- 43 miles -RRB- south of Baghdad .

Iraq has seen a sharp increase in tension between its Shiite and Sunni populations since April , when security forces raided a site used by Sunni protesters to demonstrate against the Shiite-led government .

Sunnis , who represent a minority of Iraqis , have felt politically marginalized since the overthrow of Saddam Hussein in 2003 . Shiites make up a majority of Iraqis .

So far in 2013 , more than 6,000 people have been killed in Iraq . More than 350 of those deaths came this month , and almost 1,000 happened in September .

Journalist Mohammed Adnan in Falluja contributed to this report .

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Suicide car bombing kills four police officers in al-Rutba

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Gunmen later kill three other police officers at security checkpoints in the town

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Also Tuesday , car bomb kills one person , injures 11 others in central Iraqi town of Musayyib